<html>
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>字体加粗</title>

<style>
    h1{
        font-size: 60px;
        font-weight: bold;
         
         }
</style>
</head>
<body>
    <script>
        document.write("<h1>hello world!</h1>");
    </script>

</body>
</html>